Response of respiration and nutrient availability to drying and rewetting in soil from a semi-arid woodland depends on vegetation patch and a recent wildfire

[摘要] Semi-arid woodlands, which are characterised by patchy vegetationinterspersed with bare, open areas, are frequently exposed to wildfire.During summer, long dry periods are occasionally interrupted by rainfallevents. It is well known that rewetting of dry soil induces a flush ofrespiration. However, the magnitude of the flush may differ betweenvegetation patches and open areas because of different organic mattercontent, which could be further modulated by wildfire. Soils were collectedfrom under trees, under shrubs or in open areas in unburnt and burnt sandymallee woodland, where part of the woodland experienced a wildfire whichdestroyed or damaged most of the aboveground plant parts 4 months beforesampling. In an incubation experiment, the soils were exposed to twomoisture treatments: constantly moist (CM) and drying and rewetting (DRW).In CM, soils were incubated at 80 % of maximum water holding capacity (WHC) for19 days; in DRW, soils were dried for 4 days, kept dry for another 5days, then rewetted to 80 % WHC and maintained at this water content untilday 19. Soil respiration decreased during drying and was very low in the dryperiod; rewetting induced a respiration flush. Compared to soil under shrubsand in open areas, cumulative respiration per gram of soil in CM and DRW wasgreater under trees, but lower when expressed per gram of total organic carbon (TOC). Organic mattercontent, available P, and microbial biomass C, but not available N, weregreater under trees than in open areas. Wild fire decreased the flush ofrespiration per gram of TOC in the open areas and under shrubs, and reduced TOCand microbial biomass C (MBC) concentrations only under trees, but had little effect on availableN and P concentrations. We conclude that the impact of wildfire and DRWevents on nutrient cycling differs among vegetation patches of a nativesemi-arid woodland which is related to organic matter amount andavailability.

[学科分类] 地球化学与岩石